In this work, ammonia (NH3) synthesis from N2 and H2 was carried out in a packed-bed dielectric barrier discharge (DBD) reactor, while three kinds of commercial packing materials including acidic γ-Al2O3, alkaline γ-Al2O3 and neutral alumina pellets were employed. The effect of packing materials on plasma-assisted NH3 synthesis was investigated and compared with an unpacked DBD reactor. The results show that the presence of packing materials enhanced the plasma-assisted NH3 synthesis by 15.6% to 44.4% compared to the plasma reaction without a packing. The highest NH3 concentration of 1565.5 ppm was obtained over the alkaline γ-Al2O3 packed plasma reactor. The improvement of packing materials on plasma-assisted NH3 synthesis followed the order of alkaline γ-Al2O3  >  neutral γ-Al2O3  >  acidic γ-Al2O3  >  blank tube only. A series of characterizations were performed to illustrate the structure-performance relationships between plasma-induced NH3 synthesis process and packing materials. The results showed that the basicity of the packing materials played an important role in the plasma-assisted NH3 synthesis process. The reaction mechanisms of NH3 synthesis in the packed-bed DBD reactor were also discussed.

In this study, plasma-enhanced NH 3 synthesis over a series of M/AC (M = Ru, Co, Ni, and Fe) catalysts was investigated. The combination of the plasma and activated carbon (AC) enhanced the reaction performance compared with the reaction using plasma alone. The doping of active metal on AC further improved the reaction performance by up to 37.3%. The highest NH 3 concentration of 3,026.5 ppm was obtained over Ru/AC at a specific input energy (SIE) of 12.5 kJ/ L, followed by Co/AC, Fe/AC, and Ni/AC. The highest energy efficiency of 0.72 g/ kWh was achieved at an SIE of 8.0 kJ/L when using the Ru/AC catalyst. Catalyst characterizations showed that the basicity of the M/AC catalysts plays an important role in the plasma-enhanced catalytic synthesis of NH 3. The reaction mechanism in the plasma-enh anced NH 3 synthesis was also discussed.

A series of Cu‐based spinel‐type complex oxides (CuB2O4, B=Fe, Mn, Co and Cr) was synthesized via sol‐gel method for soot combustion. The soot combustion was accelerated in the presence of all prepared CuB2O4 catalysts compared to that without catalyst. The CuCo2O4 catalyst exhibited the best catalytic activity, with the soot combustion temperatures T10, T50 and T90 of 480 °C, 539 °C and 569 °C, respectively. XRD patterns showed that the catalysts were mainly in spinel phase. The H2‐TPR, XPS and O2‐TPD characterizations revealed that the interactions between cobalt and copper led to higher content of the Cu+ species, better redox properties and abundant adsorbed oxygen species than the other three catalysts, which contributed to soot combustion. In addition, the catalytic activity of the CuCo2O4 catalysts on soot combustion were facilitated in the presence of NO, while water vapor inhibited the catalytic activity. Besides, the cycle tests clarified that CuCo2O4 catalyst exhibited good stability.

In this work, the effect of pore structure for VO x /M (M = KIT-6, SBA-15 and SiO 2 ) catalysts on plasma-catalytic soot oxidation was investigated. The combination of VO x /KIT-6 and plasma shows the highest soot oxidation rate, followed by VO x /SBA-15packed and VO x /SiO 2 -packed plasma reactor. The soot oxidation rate of 97.4 % and the energy efficiency of 0.95 g kWh À 1 can be achieved in plasma-catalytic soot oxidation over VO x /KIT-6 at 30 th min and 20 W. The catalysts were characterized by N 2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H 2 -TPR) and X-ray photoelectron spectroscopy (XPS). The results illustrated that VO x /KIT-6 and VO x /SBA-15 had large specific surface areas and good dispersion of vanadium species. The H 2 -TPR and XPS results confirmed that VO x /KIT-6 had stronger reducibility and higher relative content of O ads /(O ads + O latt ) than those of VO x /SBA-15 and VO x /SiO 2 . The good performance of soot oxidation in the plasma-catalytic systems over VO x /KIT-6 could be attributed to 1) the welldeveloped 3D mesoporous structure, which facilitated the transportation of radicals and active species, and 2) improved redox properties of VO x /KIT-6, since more active sites and surface adsorbed oxygen species on the catalyst surfaces could contribute to soot oxidation.

In this work, soot oxidation was conducted over a series of Mn-X/γ-Al2O3 (M = Ce, Co and Cu) binary catalysts in a dielectric barrier discharge reactor. The soot conversion in the plasma–catalytic system was in the order of Mn/γ-Al2O3 (57.7%) > Mn-Co/γ-Al2O3 (53.9%) > Mn-Ce/γ-Al2O3 (51.6%) > Mn-Cu/γ-Al2O3 (47.7%) during the 30 min soot oxidation process at 14 W and 150 °C. Meanwhile, the doping of Ce, Co and Cu slightly improved the CO2 selectivity of the process by 4.7% to 10.3% compared to soot oxidation over Mn/γ-Al2O3.It is worth to note that the order of CO2 selectivity was in the opposite order with soot oxidation rate. The effects of discharge power, oxygen content in the carrier gas and reaction temperature on plasma–catalytic soot oxidation was systematically analyzed. The catalyst characterizations, including N2 adsorption–desorption, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction by H2 and temperature-programmed desorption of O2, were conducted to illustrate the reaction mechanisms of plasma–catalytic soot oxidation and reaction pathways.